Ignition system

ABSTRACT

An electrical system for igniting gas burners to provide safety features as well as an efficient and dependable means for igniting the gas flame. Gas is ignited by a glow coil and a sensor- or probe-type resistance unit imposes a control function to turn off the gas supply if the burner is not ignited within a predetermined time period. The sensor also closes the gas valve whenever the sensor is no longer heated.

ilnited States Patent [56] References Cited UNITED STATES PATENTS2.318.195 5/1943 Cate 317/41 X 2.441841 7/1948 Strobel 317/132X2,549,633 4/1951 Ottmar 431/45 3,017,564 1/1962 Barney 317/41 X3,282,324 11/1966 Romanelli 431/24 Primary ExaminerFrederick L. MattesonAssistant Examiner-Robert A. Dua Attorney-Curtis, Morris & SaffordABSTRACT: An electrical system for igniting gas burners to providesafety features as well as an efficient and dependable means forigniting the gas flame. Gas is ignited by a glow coil and a sensororprobe-type resistance unit imposes a control function to turn off thegas supply if the burner is not ignited within a predetermined timeperiod. The sensor also closes the gas valve whenever the sensor is nolonger heated.

IGNITION SYSTEM This invention relates to gas burner ignition and safetycontrol systems and more in particular to a simplified electrical systemfor igniting gas burners and for cutting cutting off the gas supplywhenever malfunctioning prevents the burner from operating. An object ofthis invention is to provide improved ignition systems for gas systems.A further object is to provide electrical control systems for gasburners which provide for efficient and dependable ignition and whichprevents the objectionable results which occur when the equipmentmalfunctions. A further object is to provide inexpensive and simplecontrol systems for gas burners and the like. These and other objectswill be in part obvious and in part pointed out below.

In the drawing The single FIGURE is a schematic representation of oneembodiment of the invention.

A burner 2 is supplied with gas through a valve 4 which is opened by theenergization of a solenoid 24 but which closes automatically when thesolenoid is deenergized. Electrical power is supplied through a pair oflines 5 and 6 which extend from a control switch representedschematically at 7. The closing of switch 7 supplies electrical powerthrough lines 5 and 6 to an igniter circuit formed by the primarywinding of a transformer 8, the secondary winding of which is connecteddirectly to an igniter 10, which is in the form of a resistance heater.Power is also supplied through lines 5 and 6 to a gas supply circuitformed by a normally open switch 20, a normally closed switch 22 and asolenoid 24; and to a control circuit for switches 20 and 22.

Switches 20 and 22 are the switches of two time-delay warpswitch relayunits ll and 15, respectively, which have a control circuit connectedacross lines 5 and 6 with a resistance unit 12 and two resistance unitsor heaters 14 and 16. Relay unit 11 includes resistance heater 14 and awarp strip 13 heated thereby and operatively connected to switch 20;and, relay unit 15 is similar with resistance heater l6 heating a warpstrip 17 which operates switch 22. When strips 13 and 17 g are at'roomtemperature, switch is open and switch 22 is closed; and, the heating ofthese strips by the full energization of their resistance heaters 14 and16 causes warp strip 13 to close switch 20, and causes warp strip 17 toopen switch 22. The control circuit for switches 20 and 22 also includesa probe or sensor or resistance unit 18 which is connected in parallelwith resistance heater 16 and which has a negativeresistance-temperature characteristic. When the burner is not ignited,unit 18 is at room temperature and has relatively high resistance,however, when burner has ignited, resistance drops to a much lowerlevel. This variation in the resistance of unit 18 is used as a basiccontrol feature, based upon the high resistance detecting that theburner is not ignited.

The control circuit, formed by resistance units 16 and 18 in paralleland thence in series with resistance units 12 and 14, has a constantvoltage impressed across it when switch 7 is closed. Hence, when burner2 is not ignited, there is a predetermined distribution of that voltageinto voltages across unit 12, unit 14 and the parallel circuit of units16 and 18. However, when burner 2 is ignited and unit 18 is heated so asto have its resistance reduced, the resistance of the parallel circuitof units 16 and 18 is reduced and there is a different distribution ofthe voltage with a greater voltage across each of units 12 and 14 and alesser voltage across units 16 and 18. Also, the change in the relativeresistances of units 16 and 18 causes unit 18 to shunt a high portion ofthe total current around unit 16. The characteristics of the circuit aresuch that when burner 2 is not ignited the voltage across unit 16 andthe current flow therethrough will heat strip 17 sufficiently to openswitch 22 at the end of the time-delay period of relay unit 15, but whenburner 2 is ignited the voltage drop across unit 16 and the current flowtherethrough is not sufficient to cause strip 18 to open switch 22.

Consider now that burner 2 is to be ignited, and that switch 7 is movedto its closed position. Relay unit 11 has a 3-second time-delaycharacteristic so that it closes switch 20 3 seconds after the closingof switch 7. During that 3-second interval or time-delay period, theenergization of transformer 8 supplies current to heat igniter 10. Theclosing of switch 20 then completes a circuit through switch 22 toenergize solenoid 24 which opens valve 4 and supplies gas to burner 2.The timedelay period for unit 15 is of the order of 15 seconds so thatswitch 22 opens only atter unit 16 has been fully energized for 12seconds after switch 20 has closed. However, during that additionall2-second time-delay while the system is operating normally, burner 2receives a proper supply of gas and is ignited and it heats sensor unit18. As explained above, that heating of sensor unit 18 causesan-immediate drop in its resistance with a simultaneous drop in thecurrent flowing through unit 16. As indicated above, that drop incurrent causes a reduction in the heating of strip 17 of sufficientmagnitude to prevent the opening of switch 22. Hence, with the burneroperating properly the circuit of solenoid 24 remains energized. I

Consider now that abnormal operating conditions prevent sensor 18 frombeing heated near the end of the additional time-delay period afterswitch 20 has been closed. The current flow through unit 16 is still ata high level and warp strip 17 is heated sufficiently to cause it toopen switch 22. That breaks the circuit of solenoid 24 so that thesolenoid is deenergized and valve 4 closes automatically so as to shutoff the supply of gas to burner 2. That circuit condition is maintainedas long as power is supplied to lines 5 and 6. That is, unit 16continues to be energized sufficiently to hold switch 22 open and thatprevents the supplying of gas to the burner which in turn preventssensor 18 from being heated. The unheated sensor in turn causes thecurrent to continue to flow through unit 16. Hence, the system acts as alockout, thus preventing cycling of the type which occurs with somecontrol systems where the gas is turned on and off without beingignited. Therefore, any malfunctioning which interferes with theoperation as explained above prevents the burner from operating until ithas received attention. As an example of malfunctioning, if eitherigniter 10 or unit 18 were to become improperly positioned or defective,the energizing of the control system would result in the opening ofswitch 22 and valve 4 'would be closed. As another example, theinvention contemplates that a pilot flame could be used to ignite theburner, and a defective pilot flame would have the same effect.

The invention contemplates that the operation of the burner can becontrolled automatically. With that arrangement, any malfunctioning uponthe closing of switch 7 would lock out" the system, and a light or otheralarm would be energized to alert the user or other personnel that thesystem requires attention. In the illustrative embodiment burner 2 is aninfrared gas burner in a household appliance, and switch 7 is a standardtype of manual switch, but can be a relay switch. It is understood thatthe illustrative embodiment is adaptable for different environments andthe invention contemplates modified constructions and other arrangementswithin the scope of the claim.

lclaim:

1. in an electrical control system for a burner, the combination of, asensing resistance element having a negative temperature-resistancecharacteristic which is positioned to be heated by the burner wherebyits electrical resistance is decreased substantially when the burner isoperating normally, means constituting a supply of fuel to said burnerincluding a solenoid operated valve means, a normally closed switchconnected in series with said solenoid and providing electrical currenttherethrough to actuate said solenoid thereby to open said valve whensaid switch is closed, and a control unit operatively associated withsaid switch to open said switch, after a predetermined time delayperiod, when said control unit is energized, said control unit includingmeans for operating said switch, said operating means being connected inparallel with said sensing resistance element and having electricalresistance relative to that of said sensing resistance element such thatthe change in resistance of said sensing resistance element due to theincrease in its temperature as it is heated by said burner decreases thecurrent flow through said control unit precluding energization of saidcontrol unit thereby maintaining said switch closed.

2. An electrical control system as described in claim 1 wherein saidcontrol unit is a warp switch relay unit comprising a resistance heaterand a warp strip operatively connected with said switch and saidresistance heater of said unit is said operating means connected inparallel with said sensing resistance element. a

3. An electrical control system as described in claim 1 wherein saidburner is a gas burner and includes an igniter circuit comprising anigniter element with a transformer having its secondary windingconnected thereto.

4. A control system as described in claim 1 including a normally openswitch connected in series with said normally closed switch, a secondcontrol unit which is adapted to be energized to close said normallyopen switch and wherein said second control unit has operating meansconnected in series with the parallel circuit formed by the first-namedoperating means and said sensing resistance element 5. A control systemas described in claim 4 wherein said second control unit is a warpswitch relay unit comprising a resistance heater and a warp stripoperatively connected with said normally opened switch and saidresistance heater of said second control unit is said operating meansconnected in series with said parallel circuit.

6. A control system as described in claim 4 wherein said switches andtheir control units have time-delay characteristics whereby saidnormally open switch is closed a predetermined time after its controlunit has been energized and said normally closed switch is not openedfor a predetermined time after said normally open switch has beenclosed.

7. A control system as described in claim 6 which includes an igniterunit connected so as to be energized simultaneously with theenergization of the control unit of said normally open switch thereby torender said igniter efiective during the firsttime delay period.

8. A control system as described in claim 7 which includes a resistanceelement in series with said control unit for said normally open switch.v

9. A gas burner control system energized by electrical energy to controlthe supply of gas through a gas supply valve to said burner which isadapted to provide a certain minimum heat when operating properly,comprising, in combination, means for forming first and secondelectrical circuits, both said circuits being connected to receiveelectrical energy, said first electrical circuit having in series anormally closed switch and a control device operatively connected tosaid gas supply valve to open said valve when energy is supplied to saiddevice and to close said valve when no energy is supplied to saiddevice, said second circuit having a control operatively connected tosaid normally closed switch in said first circuit to open said switchwhen said control is energized above a predetermined energy level and tomaintain said switch closed when said control is energized below saidpredetermined energy level, a resistor having a negativeresistance-temperature characteristic such that its resistance decreaseswhen it is heated, said resistor shunting said control in said secondcircuit thereby to regulate the energy supplied to said control, wherebywhen said burner is operating properly and is supplying said certainminimum heat said resistor is heated and achieves a low resistance valuesuch that the energy level of said control is below said predeterminedenergy level and said switch remains closed and when said burner is notoperating properly and is not supplying said certain minimum heat toheat said resistor, said resistor achieves a high resistance value suchthat the energy level of said control is above said predetermined energylevel and said switch opens thereby cuttin off the energy su plied tosaid control device through said irst circuit, thus c osing said gassupply valve to said burner.

1. In an electrical control system for a burner, the combination of, asensing resistance element having a negative temperatureresistancecharacteristic which is positioned to be heated by the burner wherebyits electrical resistance is decreased substantially when the burner isoperating normally, means constituting a supply of fuel to said burnerincluding a solenoid operated valve means, a normally closed switchconnected in series with said solenoid and providing electrical currenttherethrough to actuate said solenoid thereby to open said valve whensaid switch is closed, and a control unit operatively associated withsaid switch to open said switch, after a predetermined time delayperiod, when said control unit is energized, said control unit includingmeans for operating said switch, said operating means being connected inparallel with said sensing resistance element and having electricalresistance relative to that of said sensing resistance element such thatthe change in resistance of said sensing resistance element due to theincrease in its temperature as it is heated by said burner decreases thecurrent flow through said control unit precluding energization of saidcontrol unit thereby maintaining said switch closed.
 2. An electricalcontrol system as described in claim 1 wherein said control unit is awarp switch relay unit comprising a resistance heater and a warp stripoperatively connected with said switch and said resistance heater ofsaid unit is said operating means connected in parallel with saidsensing resistance element.
 3. An electrical control system as describedin claim 1 wherein said burner is a gas burner and includes an ignitercircuit comprising an igniter element with a transformer having itssecondary winding connected thereto.
 4. A control system as described inclaim 1 including a normally open switch connected in series with saidnormally closed switch, a second control unit which is adapted to beenergized to close said normally open switch and wherein said secondcontrol unit has operating means connected in series with the parallelcircuit formed by the first-named operating means and said sensingresistance element
 5. A control system as described in claim 4 whereinsaid second control unit is a warp switch relay unit comprising aresistance heater and a warp strip operatively connected with saidnormally opened switch and said resistance heater of said second controlunit is said operating means connected in series with said parallelcircuit.
 6. A control system as described in claim 4 wherein saidswitches and their control units have time-delay characteristics wherebysaid normally open switch is closed a predetermined time after itscontrol unit has been energized and said normally closed switch is notopened for a predetermined time after said normally open switch has beenclosed.
 7. A control system as described in claim 6 which includes anigniter unit connected so as to be energized simultaneously with theenergization of the control unit of said normally open switch thereby torender said igniter effective during the first-time delay period.
 8. Acontrol system as described in claim 7 which includes a resistanceelement in series with said control unit for said normally open switch.9. A gas burner control system energized by electrical energy to controlthe supply of gaS through a gas supply valve to said burner which isadapted to provide a certain minimum heat when operating properly,comprising, in combination, means for forming first and secondelectrical circuits, both said circuits being connected to receiveelectrical energy, said first electrical circuit having in series anormally closed switch and a control device operatively connected tosaid gas supply valve to open said valve when energy is supplied to saiddevice and to close said valve when no energy is supplied to saiddevice, said second circuit having a control operatively connected tosaid normally closed switch in said first circuit to open said switchwhen said control is energized above a predetermined energy level and tomaintain said switch closed when said control is energized below saidpredetermined energy level, a resistor having a negativeresistance-temperature characteristic such that its resistance decreaseswhen it is heated, said resistor shunting said control in said secondcircuit thereby to regulate the energy supplied to said control, wherebywhen said burner is operating properly and is supplying said certainminimum heat said resistor is heated and achieves a low resistance valuesuch that the energy level of said control is below said predeterminedenergy level and said switch remains closed and when said burner is notoperating properly and is not supplying said certain minimum heat toheat said resistor, said resistor achieves a high resistance value suchthat the energy level of said control is above said predetermined energylevel and said switch opens thereby cutting off the energy supplied tosaid control device through said first circuit, thus closing said gassupply valve to said burner.